Rachel is a stunt driver, and she's escaping from a building that is about to explode! The variable $d$ models Rachel's distance from her exit (in meters) $t$ seconds after the cameras began recording the stunt. $d=-38t+220$ What is Rachel's speed?
Answer: The rate of change of the equation is $-38$, which means the distance between Rachel and her exit is decreasing by $38$ meters per second. This means Rachel is moving at a speed of $38$ meters per second toward her exit. Rachel's speed is $38$ meters per second.